Practice ammunition

ABSTRACT

Practice ammunition including a projectile formed by a thin walled frangible plastic body casing or shell having a spin-weld interconnected rear closure element and being filled with a loose mass of finely divided particulate material of substantially higher density, and preferably of relatively low animal toxicity. The plastic body casing or shell is smooth walled and formed without longitudinal grooving, and if fragmented on exit from a rifled barrel through the combined lateral forces of set-back and centrifugal force operating to radially expand the mass of particulate filler. The particulate material is partially dispersed by these same forces and further dispersed and retarded by wind resistance after leaving the barrel so as to fall to the ground within a relatively short distance from the barrel. A key slot is formed in a rear closure element for rotational locking during spin welding assembly of the body casing or shell, and a rearwardly facing annular obturator encompasses the key slot.

United States Patent 11 1 Barr et al.

[451 Jan. 15, 1974 PRACTICE AMMUNITION [73] Assignee: AAI Corporation, Cockeysville, Md.

[22] Filed: Jan. 19, 1973 [21 Appl. No.: 324,910

Related US. Application Data [63] Continuation of Ser. No. 103,079, Dec. 31, 1970,

25 24 l l w 1 1 Primary Examiner-Robert F. Stahl Att0rneyReginald F. Pippin, Jr.

[57] ABSTRACT Practice ammunition including a projectile formed by a thin walled frangible plastic body casing or shell having a spin-weld interconnected rear closure element and being filled with a loose mass of finely divided particulate material of substantially higher density, and preferably of relatively low animal toxicity. The plastic body casing or shell is smooth walled and formed without longitudinal grooving, and if fragmented on exit from a rifled barrel through the combined lateral forces of set-back and centrifugal force operating to radially expand the mass of particulate filler. The particulate material is partially dispersed by these same forces and further dispersed and retarded by wind resistance after leaving the barrel so as to fall to the ground within a relatively short distance from the barrel. A key slot is formed in a rear closure element for rotational locking during spin welding assembly of the body casing or shell, and a rearwardly facing annular obturator encompasses the key slot.

16 Claims, 4 Drawing 1F igures II II II II II II II 14 PRACTICE AMMUNITION This is a continuation of application Ser. No. l03,079 filed Dec. 31, 1970, now abandoned.

This invention relates to practice ammunition which will enable practice firing of weapons with close simulation of recoil and report, and will enable cycling of automatic or semi-automatic weapons without requirement of more expensive and dangerous standard ammunition.

It is an object of the invention to provide ammunition which is easily manufactured by molding and spin welding of the casing components, and including a projectile arrangement which enables close simulation of standard projectiles in mass and exterior size and configuration, and which upon exit from a rifled barrel will fragment and disperse within a relatively short distance while providing effectively close simulation of recoil and report as provided by standard ammunition. It is further a major feature of this invention to provide a fragmenting and distintegrating practice round as discussed previously, and which is easily manufactured.

Still other objects, features and attendant advantages will become apparent to those skilled in the art from a reading of the following detailed description of a preferred physical embodiment constructed in accordance with the invention, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial longitudinal section view of a round of ammunition according to the invention.

FIG. 2 is an enlarged longitudinal section view of the projectile of FIG. 1, and a portion of the cartridge case, chambered in a rifled barrel and prior to firing.

FIG. 3 is a schematic longitudinal section view show ing the projectile during its travel along the rifled barrel.

FIG. 4 is a rear end view of the projectile of FIG. 2.

Referring now in detail to the figures in the drawing, a cartridge 11 is provided as shown in FIG. 1 to simulate a standard or other desired cartridge having an essentially similar external configuration. Alternatively, of course, other cartridge configurations may be simulated. In the illustrative embodiment, the cartridge 11 has a case 31 housing a propellant charge 35, and a percussion primer, which cartridge case, propellant, and primer may be of conventional construction and will normally be unmodified from that of the cartridge case, propellant charge and percussion primer which is employed in the cartridge being simulated.

In the forward mouth end of the cartridge case 31 there is a projectile 21, which is the particular illustrative simulated cartridge is secured by an annular crimp 37 of the case 31 into an annular crimp groove formed in the periphery of the projectile 21. Externally the projectile 21 may be and is preferably of generally the same configuration and size as the projectile of the cartridge being simulated. However, in some instances it may be necessary, though not desirable in other respects, to elongate the projectile to some extent in order to provide the necessary mass for the projectile such as to sufficiently or more closely simulate the mass of the projectile being simulated. In many instances this elongation cannot be tolerated as such will be incompatible with the dimensional operating requirements of the weapon.

The case 31 will normally be formed of the same material as the cartridge being simulated, although it will be apparent that various materials may be employed in accordance with conventional case construction technology.

The projectile 21 is not only formed to simulate the mass and configuration of the projectile of the real cartridge being simulated, but is also constructed to have the capability and property of fragmenting and generally disintegrating into small particles upon exit from the bore of a barrel. To this end, the projectile 21, as illustrated in FIG. 2, is formed by a body shell 23, made of a plastic material such as nylon 6/6, nylon 6/12, polyethylene or polystyrene, with a wall thickness for the particular particulate material chosen such as to provide sufficient ductility of the wall to enable the main cylindrical wall portion to enlarge under radial stress to the full diameter of the rifled bore of a barrel 41 in which the cartridge is to be fired, while being of a thickness for the particular material such that upon exit from the barrel 41 the projectile 21 will fragment under the internal stresses effected by setback of a particulate filler mass 24 within the projectile body shell 23, and the centrifugal forces of the filler mass resulting from rotation of the projectile 21 about its longitudinal axis by the action of rifling 43a of the rifled bore 43. In one illustrative embodiment, a projectile casing 23 of nylon 6/6 has been employed having a wall thickness of 0.050 inch throughout its length, with the exception of a rifling band portion 25, in conjunction with a filler mass 24 of loose lead shot having particulate size diameters lying predominantly in the range of 0.012 and 0.033 inch. The body shell 23 in this instance had a length of approximately 3 inches, and an external main body diameter of approximately 0.75 inch, with an internal cylindrical main body diameter along the mid and rear sections of the projectile 23 casing of approximately 0.65 inch.

The projectile body shell 23 has formed integral therewith along a portion of the rear section thereof a rifling band 25 which protrudes radially along the exterior surface of the body shell 23 by an extent approximately equal to the radial depth of the rifling 43a, the cylindrical external diameter of the smooth wall midsection 23b and rear section 23c of the body shell 23 being approximately equal to the internal land diameter of the rifling 43a, so as to chamber within the barrel smoothly. In the illustrative embodiment mentioned above, in which the wall thickness along the major extent of the body shell 23 is 0.050 inch, the wall thickness along the rifling wall band 25 has been suitably formed as 0.070 inch. In this respect it will be noted that the internal configuration of the body shell 23 is smooth walled along its entire extent, and the body seal 23 does not require or have any pire-formed grooving. This smooth wall ungrooved construction has been found very satisfactory, and is of value in ease as well as expense of manufacture. It will also be noted that there is no cross-bracing in any area within the cavity formed by the body shell 23, including the longitudinal area of the rifling band 25, as the invention operates on a principle which enables the filler mass 24 to itself effect and maintain sufficient engagement of the rifling band 25 with the rifling 43a to effect the desired rotational motion of the projectile 21 during passage thereof along the rifled bore 43 for aiding in subse quent fragmentation and disintegration of the body shell 23 and filler mass 24.

The filler mass 24 may be loaded during manufacture through the open rear end of the body shell 23, after which this open rear end is closed by a rear closure and obturator plug 29 which is secured thereto. In the preferred construction and mode of assembly, the closure plug 29. has a reduced diameter shoulder 29b and shoulder stop 29c which fit in contigous relation with the open mouth rear end of the body seal 23, and the plug 29 is secured in place by spin welding, including rapid relative rotation of the plug or cap 29 and the body shell 23. To this end, the plug 29 has a key slot 29s formed in its rear surface, which enables rotational locking of the plug 29 during this spin welding operation. The spin weld may be effected along either or both of the shoulder 29b and stop 29c, and is preferably along both zones in order to provide a desired degree of strength so as to prevent rupture at this junction during firing and forward motion of the projectile along the barrel bore 43.

Plug 29 is provided with a tapered wall annular obturator flange extension 29a which aids in sealing of the propellant gases upon firing and upon movement of the projectile 21 along the rifled bore 43. While the rifling band 25 may also operate to some degree in this extent, the tapered wall obturator flange extension 29a is desirable as an additional precautionary measure of sealing, which may take any excess radial inward compression strain off the rifling band zone by the propellant gases during initial passage of the projectile along the rifled bore 43 immediately after firing and prior to full lateral support by the set-back and centrifugal action of the particulate filler mass 24. As noted above, this is the preferred construction, although in some instances it may be and has been found feasible to form the projectile 21 without the obturator flange extension 29a, in which instance the rifling band 25 has been found to provide sufficient scaling action with the rifled bore 43 to effect a desired forward and rotational motion of the projectile 21 through the rifled bore 43.

In designing and constructing the projectile 21, the particle material used as a filler 24 should be selected to closely proximate the density of the projectile being conventional or other projectile being simulated, which conventional projectile may be solid or otherwise formed. For instance, in the illustrative embodiment the dimensions of which are generally given above, fine sized lead shot of diameters predominantly with the range of 0.012 0.033 inch has been employed to simulate a solid steel alloy projectile having a density of 0.283 pounds per cubic inch, in which instance the loose, unpacked lead shot material as contained within the projectile body shell prior to firing has a density of approximately 0.25 pounds per cubic inch, which is sufficiently close in approximation to enable satisfactory simulation firing of the cartridge 11. In selecting the shot size of the particle material 24, various factors are considered, including packing density, maximum range, and toxicity. Shot or particles of varying sizes within a relatively small range are preferably employed, rather than a single shot size, inasmuch as such offers a better packing density than a single shot size, and this is of considerable importance in enabling the filler mass to provide sufficiently close density to the mass of the projectile being simulated.

In many instances, it is also important in selecting the particle material that a material be selected which has relatively low animal toxicity. Thus, while lead shot is acceptable in some instances and is particularly desirable from a density standpoint, in many instances it will not be acceptable in view of its high toxicity to animals, considering the propensity of various animals to ingest particle materials from the ground. Particles within the general range noted above are generally small enough to provide an acceptable maximum range, which may be of the order of meters or so, while being large enough so as to fall to the ground and not to cause an atmospheric toxicity problem.

As has been noted, the filler mass 24 occupies substantially the entire effective cavity formed by the body shell 23 and rear closure plug 29, prior to firing of the cartridge, and as shown particularly in FIG. 2. Upon firing of the cartridge 11, the projectile 21 is propelled forwardly through the rifled bore 43, and the particle mass 24 becomes longitudinally compacted under the setback forces of firing and concomitant acceleration of the projectile along the rifle bore 43. This setback compacting of the particle mass 24 causes the plastic body shell to be laterally enlarged along its cylindrical mid and rear body sections 23b, 230 as schematically illustrated in FIG. 3, and the total volume of the thus compacted particle mass 24 becomes longitudinally substantially foreshortened, also as generally indicated in this Figure. In the illustrative embodiment the resulting setback and centrifugal forces acting on the projectile 21, including the particle mass 24, result in the particle mass being foreshortened to an extent where the forward surface thereof is generally in the zone of or behind the transitional juncture zone between the tapered forward section 23a of the body shell 23 and the enlarged cylincrical mid-section 23b of the body shell 23. Thus, design problems in configuring the wall thickness of the projectile casing in the tapered forward section 23a of the casing 23 are minimized, as the lateral expansive forces exerted by the internal stresses on the particle mass 24 and the centrifugal stresses acting therethrough on the body shell 23 are primarily effected along the initial cylindrical smooth walled midsection 23b and rear section 230, as well as the rifling band zone 25 of the projectile 21. Inasmuch as the cylindrical mid'section 23b and rear section 230 have an external diameter only slightly smaller than the internal maximum or grooved diameter of the bore 43, it will be apparent that only a very small extent of stretching of the body shell will be required to accommodate the compacting of the particle mass 24 during movement of the projectile 41 along the rifled bore 43 upon firing. However, while this is the preferred design configura tion and construction, it is feasible to employ a particle density such that the forwardmost foreshortened surface of the particle mass 24 will be forwardly of the initial junction zone between the tapered forward section 230 and mid-section 23b of the body shell to some extent, as the material of the body shell 23 may be selected or conditioned such as to provide a sufficient degree of ductility to enable the further radially inwardly spaced tapered nose section adjacent this zone to be radially expanded to the bore diameter by the lateral forces resultant from particle mass setback and centrifugal action, without rupture, while still enabling subsequent rupture thereof upon exit from the barrel as a result of residual internal stresses acting through the compacted and spinning particle mass 24. For instance, the plastic material may be subjected to moisture preconditioning if so desired, as by a short period of immersion in boiling water, in order to increase its ductility to a desired degree. However, as a preferred construction, it is desirable that the fragmentation of the projectile body casing 23 be into relatively small particles after exit from the barrel, and, accordingly, it is normally most desirable to employ projectile material of relatively low moisture content, and thereby render the projectile body more brittle than would otherwise be the case with a relatively higher moisture content.

During forward motion of the projectile 21 along the rifled bore 43, it will be noted as shown in FIG. 3 that the compacting and centrifugal forces acting on and through the particulate mass 24 cause the expanded body case 23, including mid-section 23b, rifling band 25 and rear section 23c, to be seated into the zone be tween and around the rifling 43a, and it has forward motion of the projectile will effect a helical scoring of the body casing 23, which aids in the fragmentation of the body casing upon exit from the bore 43. However, it is of importance that the radial depth of the rifling 43a be such that it does not cut entirely through the laterally expanded body case 23 during this motion of the projectile along the bore 43. In the illustrative example noted above in which a body casing 23 ofa 0.050 inch wall thickness was employed, rifling of approximately 0.020 inch depth from land to groove has been found quite satisfactory, this being provided in a rifled barrel of approximately mm internal diameter.

Upon exit of the projectile 21 from the barrel, the residual internal stresses cause the plastic body case 23 to rupture and fragment, aided by the helical external grooving effected by the passage of the projectile along the rifled bore 43. The increased air resistance on the fragmented plastic parts on the body shell cause these fragmented parts to slow down and fall to the ground within a relatively short distance. Once the plastic body shell has fragmented, the compacted particulate mass 24 is dispersed in a cone around the exit of flight of the projectile under the influence of the centrifugal forces acting thereon. Thus, individual particles are subjected to increased air drag and are slowed down to an extent that they fall to the ground within a relatively short distance, as for instance less than 150 meters from the barrel. Inasmuch as the mass of the disintegrating projectile 21 may be made to be generally the same as or closely comparable to that of the projectile it is simulating, the interior ballistics of the simulated round are comparable to that of the round being simulated, and thus the recoil imparted to the gun mechanism is either the same or sufficiently comparable to be satisfactory, and the report and flash are likewise satisfactorily comparable.

While it is in all respects preferred that the round be fired in a rifled barrel as illustrated, it is possible to fire the round, with or without band 25, in a smooth bore barrel. In the instance of a smooth bore fired projectile, the break-up of the projectile will be accomplished solely by the setback forces which effect corresponding lateral rupture forces on the projectile case as it emerges from the barrel, as distinguished from both setback derived lateral forces and centrifugal forces in the case of projectiles fired through a rifled barrel as in the illustrated mode of practice. However, in utilizing this alternative firing mode, it will normally be found that the projectile will rupture and fragment with a fair degree of dissemination of the particulate material. Nevertheless, the major body of the particulate material appears to remain within a generally substantially smaller cone dispersal pattern. For instance, with the rifled barrel mode of practice of the invention, the particulate material is found to be acceptably dispersed and distributed within a cone angle of approximately 15 to 20, using a conventional 7 degree rifling in a 20 mm barrel bore, and this has been found to yield a cone dispersion of 5 feet radius at a 50 foot range, whereas with a non-rifled smooth bore barrel employing the same projectile, with or without a rifling band, the pattern is substantially much more concentrated within a smaller cone angle, and with the greater volume of particulate material within an even smaller cone angle in this instance.

As has been noted, the loose filler mass initially effectively filling the cavity formed within the body casing 23 may be formed of various materials, one illustrative embodiment of which is lead shot. Alternatively and in many instances more preferable from the standpoint of animal toxicity, although in some instances substantially less preferable from the standpoint of density re quirements, one may employ iron or steel particles, also preferably in the form of multiple sized shot which may be of approximately the same size as that mentioned above in the case of lead shot. Also, various other materials may be employed in a given instance where the conditions merit, including tugsten, copper, brass, etc.

While the invention has been described with respect to a single preferred embodiment, it will be apparent that various modifications and improvements may be made within the scope and spirit of the invention. Accordingly, the invention is not to be limited by the particular illustrative embodiment, but only by the scope of the appended claims.

We claimi 1. Disintegrating practice ammunition, comprising a projectile having a frangible body shell of moldable and spinweldable material,

said body shell forming a tapered nose section and a generally cylindrical mid and rear section,

said body shell being hollow and forming a cavity for containing a mass of loose particulate filler material,

a closure element closing the rear of said body shell whereby said cavity is a closed cavity,

an exterior rifling band on said body shell and protruding radially beyond the remainder of said generally cylindrical mid and rear section,

a mass of finely divided particulate relatively high density filler material container within and gener ally filling the effective volume of said cavity,

a circumferential spin weld interconnection formed between and joining said body shell and said closure element,

said closure element having a key slot formed in its rear surface for rotational locking to assist in enabling spin-welding assembly of said body shell and said closure element.

2. Disintegrating practice ammunition according to claim ll,

further comprising an annular rearwardly extending obturator extension formed at the rear of said body shell and encompassing said key slot.

3. Disintegrating practice ammunition according to claim 2,

said obturator extension being an integral part of said closure element and being rearwardly and outwardly tapered. 4. Disintegrating practice ammunition according to claim 3,

said key slot being a laterally extending recess. 5. Disintegrating practice ammunition according to claim 2,

said key slot being a laterally extending recess. 6. Disintegrating practice ammunition according to claim 1,

said closure element closing the rear of said body shell being a plug having an outer cylindrical diameter corresponding to the adjoining rear section of said body shell. 7. Disintegrating practice ammunition according to claim 6,

said plug having a reduced diameter shouldered forward end and a cup-shaped rear end, said cup-shaped rear end of said plug having a tapered annular wall forming said obturator extension, said body shell seating and being secured in peripheral sealing relation on said shouldered forward end of said plug. 8. Disintegrating practice ammunition according to claim 1,

said mass of particulate material being compactible and said body shell being radially effectively expandable under set-back forces to effect a compacted and reduced length volume of said mass during passage of said projectile along a rifled bar rel bore and having a forward surface lying approximately in the zone of or behind the effective zone of intersection between the tapered nose section and said generally cylindrical mid section of said body shell. 9. Disintegrating practice ammunition according to claim 1,

a cartridge case having an ignitable propellant charge therein, and means releasably securing said projectile at the forward end of said cartridge case. 10. Disintegrating practice ammunition according to claim 9,

said body shell having an annular groove formed therein rearwardly of said rifling band, and said cartridge case being secured to said projectile by an annular crimp of said case into said groove, the forward end of said case abutting and being of substantially the same diameter as said rifling band, said rifling band being integrally unitary with said body shell. 11. Disintegrating practice ammunition according to claim 10,

said mass of finely divided particulate filler being of multiple size predominantly within a relatively narrow range of approximately 0.012 to 0.033 inch in diameter. 12. Disintegrating practice ammunition, comprising a projectile having a frangible body shell, said body shell forming a tapered nose section and a generally cylindrical mid and rear section, said body shell being hollow and forming a cavity for containing a mass of loose particulate filler material, and means closing the rear of said body shell whereby said cavity is a closed cavity, and an exterior rifling band on said body shell and protruding radially beyond the remainder of said generally cylindrical mid and rear section, said cavity being devoid of lateral bracing there within, and a mass of finely divided loose particulate relatively high density malleable filler material contained within and generally filling the effective volume of said cavity, said mass of particulate material being compactible and said body shell being radially effectively expandable under set-back forces to effect a compacted and reduced length volume of said mass during passage of said projectile along a rifled barrel bore and having a forward surface lying approx imately in the zone of or behind the effective zone of intersection between the tapered nose section and said generally cylindrical mid section of said body shell. 13. Disintegrating practice ammunition according to claim 12,

said mass of finely divided particulate malleable filler being minute individually discrete metal shot, and said body shell being formed of plastic material. 14. Disintegrating practice ammunition according to claim 13,

said metal filler shot being selected from materials which are generally of low animal toxicity. 15. Disintegrating practice ammunition according to claim 12,

said mass of finely divided particulate malleable filler being of multiple size discrete metal shot predominantly within an approximate size range of approximately 3 to l. 16. Disintegrating practice ammunition according to claim 12,

said mass of finely divided particulate filler being multiple size predominantly within a range of approximately 0.012 to 0.033 inch in diameter.

l l l= UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,785,293

A Januar 15 1974 D TED Irwin Barr; Nicholar J. La Costa; INVENTOR(S) William 0. Davis It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown betow:

Column 1, Line 51, Change "is" (second occurrence) to in Column 3, Line 47, Change "with" to within Column 4, Line 33, Change "cylincrical" to cylindrical Signed and Scaled this mmem Day of A ines:

[SEAL] Anm:

RENE D. TEGTMEYER UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,785,293

DATED Januar 15, 1974 Irwin ..Barr; Nicholar J. La Costa; INVENTOR(S) William 0. Davis It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Column 1, Line 51, Change "is" (second occurrence) to in Column 3, Line 47, Change "with" to within Column 4, Line 33, Change "cylincrical" to cylindrical Signed and Scaled this Fourteenth D a y of April I 98! [SEAL] Attest:

RENE D. TEGTMEYIER Attestittg Oflicer Acting Commissioner of Patents and Trademarks 

1. Disintegrating practice ammunition, comprising a projectile having a frangible body shell of moldable and spinweldable material, said body shell forming a tapered nose section and a generally cylindrical mid and rear section, said body shell being hollow and forming a cavity for containing a mass of loose particulate filler material, a closure element closing the rear of said body shell whereby said cavity is a closed cavity, an exterior rifling band on said body shell and protruding radially beyond the remainder of said generally cylindrical mid and rear section, a mass of finely divided particulate relatively high density filler material container within and generally filling the effective volume of said cavity, a circumferential spin weld interconnection formed between and joining said body shell and said closure element, said closure element having a key slot formed in its rear surface for rotational locking to assist in enabling spinwelding assembly of said body shell and said closure element.
 2. Disintegrating practice ammunition according to claim 1, further comprising an annular rearwardly extending obturator extension formed at the rear of said body shell and encompassing said key slot.
 3. Disintegrating practice ammunition according to claim 2, said obturator extension being an integral part of said closure element and being rearwardly and outwardly tapered.
 4. Disintegrating practice ammunition according to claim 3, said key slot being a laterally extending recess.
 5. Disintegrating practice ammunition according to claim 2, said key slot being a laterally extending recess.
 6. Disintegrating practice ammunition according to claim 1, said closure element closing the rear of said body shell being a plug having an outer cylindrical diameter corresponding to the adjoining rear section of said body shell.
 7. Disintegrating practice ammunition according to claim 6, said plug having a reduced diameter shouldered forward end and a cup-shaped rear end, said cup-shaped rear end of said plug having a tapered annular wall forming said obturator extension, said body shell seating and being secured in peripheral sealing relation on said shouldered forward end of said plug.
 8. Disintegrating practice ammunition according to claim 1, said mass of particulate material being compactible and said body shell being radially effectively expandable under set-back forces to effect A compacted and reduced length volume of said mass during passage of said projectile along a rifled barrel bore and having a forward surface lying approximately in the zone of or behind the effective zone of intersection between the tapered nose section and said generally cylindrical mid section of said body shell.
 9. Disintegrating practice ammunition according to claim 1, a cartridge case having an ignitable propellant charge therein, and means releasably securing said projectile at the forward end of said cartridge case.
 10. Disintegrating practice ammunition according to claim 9, said body shell having an annular groove formed therein rearwardly of said rifling band, and said cartridge case being secured to said projectile by an annular crimp of said case into said groove, the forward end of said case abutting and being of substantially the same diameter as said rifling band, said rifling band being integrally unitary with said body shell.
 11. Disintegrating practice ammunition according to claim 10, said mass of finely divided particulate filler being of multiple size predominantly within a relatively narrow range of approximately 0.012 to 0.033 inch in diameter.
 12. Disintegrating practice ammunition, comprising a projectile having a frangible body shell, said body shell forming a tapered nose section and a generally cylindrical mid and rear section, said body shell being hollow and forming a cavity for containing a mass of loose particulate filler material, and means closing the rear of said body shell whereby said cavity is a closed cavity, and an exterior rifling band on said body shell and protruding radially beyond the remainder of said generally cylindrical mid and rear section, said cavity being devoid of lateral bracing therewithin, and a mass of finely divided loose particulate relatively high density malleable filler material contained within and generally filling the effective volume of said cavity, said mass of particulate material being compactible and said body shell being radially effectively expandable under set-back forces to effect a compacted and reduced length volume of said mass during passage of said projectile along a rifled barrel bore and having a forward surface lying approximately in the zone of or behind the effective zone of intersection between the tapered nose section and said generally cylindrical mid section of said body shell.
 13. Disintegrating practice ammunition according to claim 12, said mass of finely divided particulate malleable filler being minute individually discrete metal shot, and said body shell being formed of plastic material.
 14. Disintegrating practice ammunition according to claim 13, said metal filler shot being selected from materials which are generally of low animal toxicity.
 15. Disintegrating practice ammunition according to claim 12, said mass of finely divided particulate malleable filler being of multiple size discrete metal shot predominantly within an approximate size range of approximately 3 to
 1. 16. Disintegrating practice ammunition according to claim 12, said mass of finely divided particulate filler being multiple size predominantly within a range of approximately 0.012 to 0.033 inch in diameter. 